Stimulation of renin release by hyperoncotic perfusion of the isolated rat kidney.

Renin release was measured in the isolated rat kidney perfused with a recirculating artificial medium containing bovine serum albumin at 6.7 g per 100 ml of 11 g per 100 ml. At the higher concentration of albumin, glomerular filtration ceased and the rate of renin release over 70 minutes of perfusion was increased 6-fold. The addition of ouabain to the perfusate containing 11 g per 100 ml inhibited the release of renin, suggesting that inhibition of Na-K-ATPase or the related changes in cellular volume or composition prevented renin release. Lowering the osmolality of the perfusate by reducing the concentration of sodium chloride also prevented the increase in renin secretion produced by perfusion with 11 g per 100 ml albumin. Increasing the osmolality of the perfusate with mannitol restored the augmented renin release. These results are consistent with the hypothesis that alterations in the volume of certain cells, perhaps in the juxtaglomerular apparatus itself, can control renin release.